The Study On Space-Time Coding About Wireless Communications

The third generation wireless communication systems require higher communication quality and transmission rate than cellular wireless standard, which made people develop more effective technology of coding, modem, and signal process to improve quality and spectrum efficiency. Space-time coding technology is a good scheme. This technique is mainly designed to combat fading by combining the technique of channel coding and antenna diversity, hence increasing the capacity of wireless communications systems .Space-time coding combines signal processing with coding techniques appropriate to multiple transmit antenna and provides significant gain. It is a new solution to satisfy high data-rate of wireless communications in the future.Space-time coding includes layered space-time coding(LSTC), space-time treills coding(STTC) and space-time block coding(STBC). LSTC has high spread using but the performance is not good against fading. STTC has good performance but high decode complexity. And STBC is a kind of STC with simple structure, and its easy implement and its good compatibility. This thesis focuses on STBC's performance and its applications. The main contents are as follows:(1) The simple squaring decode algorithm of STBC is studied in depth and get the expression of instant-signal-to-noise at the receiver and deduced the closed expression of STBC's SER(symbol error probability) combing the expression of SER under white noise channel under MPSK and MQAM modulation when the channel is Rayleigh fading. And also analyse the performance through numerical simulation using Matlab.(2) Based on careful study on the channel capacity under rayleigh fading, we deduced the expression of STBC's channel capacity under rician fading and get upper bound with increasing the number of transmit antenna when the receive antenna is fixed. The result of comparison to the capacity under rayleigh fading channel is useful when STBC is applied to practical communication system. (3) There exists an error floor of STBC through studying on its perfor- mance on time-selective fading channel. We analysis the reason and proposed two new decode combination scheme to eliminated the error floor and the performance of STBC on time-selective fading channel is improved.